linux-kernel - Re: [PATCH] tpm: ibmvtpm: Call tpm2_sessions

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Message-ID: <e7db74a0-cd5c-4394-b87e-c31ea0861ea1@linux.ibm.com>
Date: Mon, 1 Jul 2024 15:14:43 -0400
From: Stefan Berger <stefanb@...ux.ibm.com>
To: Jarkko Sakkinen <jarkko.sakkinen@....fi>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Linux regressions mailing list <regressions@...ts.linux.dev>
Cc: naveen.n.rao@...ux.ibm.com, linux-kernel@...r.kernel.org,
        linux-integrity@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] tpm: ibmvtpm: Call tpm2_sessions_init() to initialize
 session support



On 7/1/24 15:01, Jarkko Sakkinen wrote:
> On Mon Jul 1, 2024 at 6:29 PM UTC, Stefan Berger wrote:
>>
>>
>> On 7/1/24 11:22, Jarkko Sakkinen wrote:
>>> On Fri, 2024-06-28 at 17:00 +0200, Linux regression tracking (Thorsten Leemhuis) wrote:
>>>> [CCing the regression list]
>>>>
>>>> On 20.06.24 00:34, Stefan Berger wrote:
>>>>> Jarkko,
>>>>>     are you ok with this patch?
>>>>
>>>> Hmmm, hope I did not miss anythng, but looks like nothing happened for
>>>> about 10 days here. Hence:
>>>>
>>>> Jarkko, looks like some feedback from your side really would help to
>>>> find a path to get this regression resolved before 6.10 is released.
>>>>
>>>> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
>>>
>>> Sorry for latency, and except a bit more slow phase also during
>>> July because I'm most of this month on Holiday, except taking care
>>> 6.11 release.
>>>
>>> This really is a bug in the HMAC code not in the IBM driver as
>>> it should not break because of a new feature, i.e. this is only
>>> correct conclusions, give the "no regressions" rule.
>>>
>>> Since HMAC is by default only for x86_64 and it does not break
>>> defconfig's, we should take time and fix the actual issue.
>>
>> It was enabled it on my ppc64 system after a git pull -- at least I did
>> not enable it explicitly. Besides that others can enable it on any arch
>> unless you now change the 'default x86_64' to a 'depends x86_64' iiuc
>> otherwise the usage of a Fixes: , as I used in my patch, would be justified.
>>
>> config TCG_TPM2_HMAC
>> 	bool "Use HMAC and encrypted transactions on the TPM bus"
>> 	default X86_64
>> 	select CRYPTO_ECDH
>> 	select CRYPTO_LIB_AESCFB
>> 	select CRYPTO_LIB_SHA256
>>
>> https://elixir.bootlin.com/linux/v6.10-rc6/source/drivers/char/tpm/Kconfig
> 
> Yep, it is still a bug, and unmodified IBM vtpm driver must be expected
> to work. I was merely saying that there is some window to  fix it properly
> instead of duct tape since it is not yet widely enable feature.
> 
> I was shocked to see that the implementation has absolutely no checks
> whether chip->auth was allocated. I mean anything that would cause
> tpm2_sessions_init() not called could trigger null dereference.
> 
> So can you test this and see how your test hardware behaves:

I just tested it and it does NOT resolve the issue on my ppc64 machine. 
I see this here:

[    1.549798] tpm_ibmvtpm 5000: CRQ initialized
[    1.549871] tpm_ibmvtpm 5000: CRQ initialization completed
[    2.569446] tpm2_start_auth_session: encryption is not active
[    2.570544] tpm tpm0: A TPM error (154) occurred attempting get random
....
[  330.188826] tpm tpm0: A TPM error (149) occurred attempting extend a 
PCR value
[  330.189438] ima: Error Communicating to TPM chip, result: 149
[  330.195007] tpm tpm0: A TPM error (149) occurred attempting extend a 
PCR value
[  330.195550] ima: Error Communicating to TPM chip, result: 149
[  330.197246] tpm tpm0: A TPM error (149) occurred attempting extend a 
PCR value
[  330.197727] ima: Error Communicating to TPM chip, result: 149
[  330.199378] tpm tpm0: A TPM error (149) occurred attempting extend a 
PCR value
[  330.199962] ima: Error Communicating to TPM chip, result: 149
[  330.201452] tpm tpm0: A TPM error (149) occurred attempting extend a 
PCR value
[  330.201917] ima: Error Communicating to TPM chip, result: 149


My 4-liner patch, applied on top of it, does resolve the issue:

[    1.462079] tpm_ibmvtpm 5000: CRQ initialized
[    1.462125] tpm_ibmvtpm 5000: CRQ initialization completed
[    2.496024] xhci_hcd 0000:00:02.0: xHCI Host Controller
[    2.496183] xhci_hcd 0000:00:02.0: new USB bus registered, assigned 
bus number 1

Applying it is probably the better path forward than restricting HMAC to 
x86_64 now and enabling it on a per-architecture basis afterwards ...

    Stefan

> 
> https://lore.kernel.org/linux-integrity/20240701170735.109583-1-jarkko@kernel.org/T/#u
> 
> I'll modify it accrodingly if problems persist. Please put your feedback
> over there. I cannot anything but compile test so it could be that
> I've ignored something.
> 
> BR, Jarkko